Fischer coupler-gelatin compositions



United States Patent 3,551,151 FISCHER COUPLER-GELATIN COMPOSITIONS Rodwick L. Malau, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed July 31, 1967, Ser. No. 657,044 Int. Cl. G03c 1/76; G03c 1/02 US. C]. 96-74 14 Claims ABSTRACT OF THE DISCLOSURE Fischer coupler-gelatin compositions in which the gelatin has an isoelectric point of at least 6.5 have substantially lower viscosities than compositions of the same couplers and gelatins having isoelectric points below 6.5 and are used to advantage to incorporate Fischer couplers in light-sensitive silver halide gelatin emulsions.

The present invention relates to photography. More particularly, the invention relates to methods and compositions for incorporating color couplers in photographic emulsions, to the emulsions so prepared, and to photographic elements provided with such emulsions. Still more particularly, the invention relates to methods and compositions for providing photographic color couplers containing acidic solubilizing groups in gelatin silver halide emulsions, to the emulsions so produced, and to photographic elements provided with one or more of such emulsions.

Photographic color couplers have been extensively described in the literature. A wide variety of couplers have been found which react with the oxidation product of a silver halide developer to form dyes useful in photography. The couplers are generally divided into two groups; phenolic and active methylene. The phenolics are derived chiefly from phenol and a-uaphthol and the coupling position is at the para carbon atom. The active methylene types are generally either open or closed chain and the coupling position is the methylene group adjacent to an electron attracting atom or group. The photographic phenolic couplers are generally cyan-formers. Cyclic active methylene couplers include the S-pyrazolone magenta-formers. Open-chain active methylene couplers include magenta acylacetonitriles and yellow acylacetamides, cyanoacetyls, acylacetanilides and 1,3-diketones.

As is well-known in the art, color coupling can take place by replacing a hydrogen atom at the reactive center of the coupler molecule or by replacing a non-hydrogen substituent at the reactive center. Where a non-hydrogen substituent is replaced, the couplers undergo what is usually referred to as .elimination coupling and this system has certain distinct advantages. For example, the dye-forming reaction may require only two molecules of silver halide per molecule of dye formed instead of the four required with an unsubstituted coupler such as a phenol coupler. Such substituted couplers are classified as Z-equivalent couplers whereas the unsubstituted couplers are classified as 4-equivalent. A further distinct advantage of elimination couplers is in the case where the coupler is required to be only temporarily nondiffusing. In this case, a ballast group which renders the coupler non-diffusing is chemically combined with the substituent which is split from the coupler during development. The dye formed, therefore, has no ballast group and is thus diffusible.

The couplers are usually modified in any of several ways to confer desirable properties dictated, for example, by the manner in which the coupler is to be used. For example, if the coupler is to be used in a developer solution, it must be soluble therein and be able to penetrate ice gelatin layers. Thus, a small molecule is required. However, if the coupler is to be provided permanently in an emulsion layer, it should be compatible with the emulsion but should not diffuse therefrom. Thus, a large molecule is required and, to this end, high molecular weight ballast groups are provided in the molecule which prevent diffusion thereof. Still further, in some photographic systems, the coupler is non-diffusing until development at which time the dye formed is intended to migrate from the emulsion to another layer such as a mordanted receiver sheet to which the migrating dye becomes fixed.

In the case where the coupler is provided in the emulsion layer, either in the diffusible, non-diffusible, or temporarily non-diffusible state, it may be added directly or preblended with a suitable carrier. Where the carrier is aqueous, such as a gelatin composition, or where the coupler is added directly to the phtographic gelatin silver halide emulsion, it must be soluble and compatible with gelatin and, to this end, large coupler molecules are provided wtih one or more acidic solubilizing groups such as sulfonic acid, carboxylic acid, and alkali metal and ammonium salts thereof. It has proven diflicult, however, to incorporate couplers containing the mentioned solubilizing groups in photographic emulsions due to the high viscosity of the emulsion formed.

It is an object of the present invention to provide gelatin silver halide emulsions with color couplers containing solubilizing groups and without the mentioned disadvantage of high emulsion viscosity previously occasionedby incorporating such couplers in these emulsions. It is a further object of the invention to provide improved compositions and methods for blending such color couplers with photographic emulsions. It is still a further object to provide photographic elements including said emulsions coated thereon.

These and other objects are achieved according to my invention by providing a photographic color coupler composition comprising a coupler that contains at least one solubilizing group and gelatin having an isoelectric point of at least 6.5. My couplers are advantageously dispersed in my gelatins. The viscosity of my dispersions is substantially lower than identical dispersions of the same coupler with gelatin having a lower isoelectric point. When a dispersion according to the invention is incorporated in a photographic emulsion, that emulsion is more easily coated on a photographic substrate because the viscosity thereof is lower than similar emulsions containing the same couplers dispersed in gelatin having a low isoelectric point.

The photographic color-forming couplers used to advantage according to my invention are often referred to as Fischer couplers. They are non-diffusing couplers that are made non-diffusing by having substituted on the coupler any of the known ballast groups such as bulky organic groups or alkyl groups having more than 5 carbon atoms, and an acid solubilizing group, e.g., sulfo, carboxy, etc., and their alkali metal salts. The ballasting group is advantageously attached to the coupler at a carbon atom in a non-coupling position or attached to the carbon in the coupling site through a group which couples off upon reaction with an oxidized color developing agent. The solubilizing group (or groups) is advantageously attached to the ballast group, to a non-ballasting group or directly to the coupler providing it does not interfere with the dye-forming coupler reaction, both 4-equivalent and Z-equivalent couplers are used to advantage.

Any of the well-known acid group solubilized nonditfusing 4-equivalent and Z-equivalent open-chain active methylene containing couplers are used to advantage as yellow dye formers according to my invention. These couplers include the cyanoacetyl couplers (such as, the

cyanoacetylcoumarone couplers, the cyanoacetylbenzoyl couplers, the heterocyclicacetonitrile couplers, etc.), the open-chain ketomethylene couplers, such as, the acylacetyl couplers (e.g., the acylacetanilide couplers, the acylacetanilide couplers include the alkoylacetanilide couplers, the aroylacetanilide couplers, the pivalylacetanilide couplers, etc. The acylacetamide couplers include the alkoylacetamide couplers, the arolyacetamide couplers, the pivalylacetamide couplers, etc.

These 4-equivalent open-chain couplers include those represented advantageously by the formula:

R C OH2X wherein R represents an alkyl group (substituted or not), an aromatic group (substituted or not), a heterocyclic group (substituted or not), etc., and X represents the cyano group, a carbamyl group (substituted or not), etc. such that at least one of R and X contains substituents which ballast the coupler and makes it non-dilfusing in hydrophilic colloid layers, and at least one of R and X contains at least one solubilizing group, e.g., sulfo carboxy or alkali metal salt thereof.

Typical 4-equivalent yellow-forming couplers include the following:

( 1 N-amyl-p-benzoylacetaminobenzenesulfonate (2) nonyl-p-benzoylacetaminobenzenesulfonate (3) 4-sulfobenzoyl-2-hexadecyloxy-S-sulfoacetanilide dipotassium salt (4) 4- (N-methyl-N-octadecyl) -cyanoacetarnidobenzene- 3-carboxylic acid (5 a-benzoyl-a- 3-octadecylcarbamylphenylthio -3,5-

dicarboxyacetanilide (6) ot-PiVEtlYl-oc- 3-octadecylcarbamylphenylthio) -4- sulfoacetanilide potassium salt The 2-equivalent yellow-forming couplers are derived from the general types of parent 4-equiva1ent couplers by replacing one of the two hydrogen on the alpha-carbon (i.e., methylene) with any coupling 01f group including groups such as the fluorine atom, the chlorine atom, an acyloxy group, a cyclooxy group and a thiocyano group. Typical 2-equivalent couplers used to advantage included the alpha-fluoro couplers of U.S. Pat. 3,277,155, the achloro couplers of U.S. Pat. 2,778,658, the tat-thiocyano couplers of U.S. Patent 3,253,924, the u-acyloxy couplers of Loria U.S. patent application 477,353, filed July 26, 1965, the u-cyclooxy couplers of Loria U.S. patent application 469;887, filed July 6, 1965, now U.S. Pat. 3,408,194, and a-alkthio, u-arylthio u-alkoxy and OL-(SllbStltllt6d azo) couplers of the type shown in Whitmore et al U.S. Pat. 3,227,550.

The Z-equivalent open-chain yellow-forming couplers include those represented by the formula:

wherein R and X are as described previously; Y is a coupling 01f group, such as, the chlorine atom, the fluorine atom, the thiocyano group, an acyloxy group [e.g., an alkoyloxy group (substituted or not), an aroyloXy group (substituted or not), a heterocycloyloxy group (substituted or not), etc., in which the groups are substituted with a wide variety of well-known groups and also a group in which R and X are as described previously], and a cyclooxy group [e.g., an aryloxy group (e.g., a phenoxy group, a naphthoxy group, a heterocycloXy group (e.g., a pyridinyloxy group, a tetrahydropyranyloxy group, a tetrahydroquinolyloxy group, etc.) an alkoXy group, an alkthio group and arylthio group in which these groups are advantageously substituted with a wide variety of well-known groups and also a group in which R and X are as defined previously.

Typical illustrative examples of 2-equivalent yellowforming couplers include the following:

( l Ct- [4- N-rnethyl-N-octadecylsulfamyl phenoxy] -04- pivalyl-4-sulfoacetanilide potassium salt (2) a-pivalyl-a-(4-sulfophenoxy) -4- (N-methyl-N-octadecylsulfamyy) acetanilide potassium salt (3 a-(o-methoxybenzoyl) -4- [5-(2-carboXy-x-chlorosulfonylbenzamido -2- (2,4-di-t-amylphenoxy) benzamido]-2-n1ethoxyacetanilide (4) ot-pivalyl-ot-(3-octadecylcarbamylphenylthio -4-sulfoacetanilide potassium salt (5 OC-bCHZOYl-Ot- (4-hydroXy-Z-pentadecylphenylazo -4- (3-sulfobenzamido acetanilide sodium salt (6) ot-bCIlZOYl-oc- (4-hydroxy-2-pentadecylphenylazo) -4- 3,5 -disulfobenzarnido) acetanilide dipotassium salt (7) ot-benzoyl-a- [4- 3-methyl-5-pentadecyl pyrozolylazo] -4- 3,5 -disulfobenzamido acetanilide dipotassium salt Any of the well-known acid group solubilized nondiffusing substituted S-pyrazolone couplers that are incorporated in photographic emulsion layers are used to advantage as the magenta-dye-former according to my inyention.

The 4-equivalent magenta-forming couplers used according to my invention includes those having the formu- 1a:

wherein R is as described previously and R represents a group such as an alkyl group, a substituted carbamyl group, an amino group (substituted or not with one or two alkyl groups and/ or one or two aryl groups), a substituted amido group, e.g., a benzamido group (substituted or not), an alkamido group (substituted or not), etc., such that at least one of R and R contains a ballast group and at least one of R and R contians a sulfo group, a carboXy group or an alkali metal salt thereof.

Typical illustrative examples of 4-equivalent magentaforming couplers include the following:

( 1 3-heptadecyl-1- (4-phenoXy-3-sulfophenyl) S-pyrazolone (2) 1-( p-sulfo-m-heptadecyl)-3-carboxymethyl- S-pyrazolone sodium salt (3) 1-(4-sulfophenyl) -3-(4-sulfo-3-heptadecylamino)- 5-pyrazolone dipotassium salt (4) 1- [4-( 3,5 -dicarboxylbenzamido)-3-octadecylphenyl] -3-ethoxy-5-pyrazolone The 2-equivalent couplers are derived from the 4-equivalent parent couplers by replacing one of the hydrogens on the carbon in the 4-position of the pyrazolone ring with a coupling ofl. group. Examples of coupling off groups used to advantage in 2-equivalent magenta-forming couplers are the thiocyano group illustrated by the couplers in Loria U.S. Pat. 3,253,924 and the acyloxy group containing 2-equivalent magenta-forming couplers of Loria U.S. Patent application 247,302, now U.S. Patent 3,311,476. The other coupling off groups include acyl oxy, aryloxy, alkoxy, arylthio, alkylthio, and substituted azo such as are shown in Whitmore et al. U.S. Pat. 3,227,- 550, the chlorine atom, the fluorine atom, and the sulfo group.

The Z-equivalent magenta-forming couplers used according to my invention include those having the formula:

wherein R and R' are as defined previously; and Y represents a coupling off group, such as, the thiocyano group, an acyloxy group, an aryloxy group, an alkoxy group, an alkylthio group, an arylthio group, the chlorine atom, the fluorine atom, the sulfo group, etc.

Typical illustrative examples of Z-equivalent magentaforming couplers include the following:

( l l-(2,4,6-trichlorophenyl)-3-pentadecyl- 4-sulfo-5-pyrazolone (2) l-(4-sulfophenyl) )-3-(4-su1foanilino)-4-(2-hydroxy-4-pentadecyl)phenylaZo-5-pyrazolone dipotassium salt (3 3-pentadecyl-1- (4-phenoxy-3 -sulfphenyl) 4-(4-tolylsulfonylphenylazo) --pyrazolone (4) 3-heptadecyl-1- (4-phenoxy-3-sulfophenyl) 4- (4-tolylsulfamylphenylazo) -5-pyrazolone (5 1- (p-sulfophenyl) -3-carboxymethyl-4- 4-hydroxy- 2-pentadecylphenylazo -5-pyrazolone sodium salt ('6) 1- 4-sulfophenyl) -3-carboxy-4- (4-hydroxy- Z-pentadecylphenylazo) -5-pyrazolone sodium salt (7) 1-(4-sulfophenyl) -3-(4-sulfonamino) -4-(2-hydroxy-4-pentadecylphenylazo -5-pyrazolone dipotassium salt (8) 1- [4-( 3,5-dicarboxylbenzamido)phenyl] 3-ethoxy- 4- 3-octadecyl-carbamylphenylthio -5-pyrazolone Any of the well-known acid group solubilized non-diffusing 4-equiva1ent phenolic and naphthoic cyan-forming couplers can be used to advantage as the cyan dye former.

The 4-equivalent cyan-forming couplers used according to my invention include those having the formulas;

v OH and VI 0H wherein R represents hydrogen, an alkyl group, an aryl group, a heterocyclic group, an amino group( e.g., amino, alkylamino, arylamino, heterocyclic amino, etc.), a substituted carbonamido group (e.g., an alkylcarbonamido group, an arylcarbonamido group, and a heterocyclicarbonamido group), a substituted sulfonamido group (e.g., an alkylsulfonamido group, an arylsulfonamido group, a heterocyclicsulfonamido group, etc.), a substituted sulfamyl group (e.g., an alkylsulfamyl group, an arylsulfamyl group, a heterocyclic sulfamyl group, etc.), a substituted carbamyl group (e.g., an alkylcarbamyl group, an arylcarbarnyl group, a heterocyclic carbamyl group, etc.), etc.; and R R and R each represent any of the groups represented by R and in addition the chlorine atom, an alkoxy group, etc., such that at least one of R R R and R is substituted by any of the ballasting groups well-known in the art and at least one of R R R and R contains at least one sulfo group, carboxy group or alkali metal salt thereof.

Typical 4-equivalent cyan-forming couplers include the following illustrative examples:

( 1) 2-carboxy-6-pentadecylureylenephenol (2) 2- [2- (pentadecylsulfonyl -3- sulfophenyl) carbamyl] naphthol 3 Z-pentadecylureylenephenol 4) 2- [2- (pentadecyloxyphenyl) carbamyl] naphthol (5 1-hydroxy-N{4- [5 Z-carboxy-x-chlorosulfonylbenzamido 2- 2,4-di-t-amylphenoxy) benzamido] phenethyl}-2-naphthamide Any of the Well-known acid group solubilized non-diffusing 2-equivalent cyan-forming couplers known in the art for incorporation in photographic layers may be used to advantage. Usually the Z-equivalent couplers are derived from the corresponding 4-equivalent couplers by substituting a coupling off group on the carbon in the 4- position of the phenolic or naphthoic ring. Included among the coupling oil groups are the acyloxy group illustrated by the 4-acyloxyphenols and 4-acyloxynaphthols of Loria U.S. Patent application 247,302, filed Dec. 26, 1962, now U.S. Pat. 3,311,476, the cyclooxy group illustrated by the 4-cyclooxy naphthols of Loria U.S. Patent application 483,807, filed Aug. 30, 1965, now U.S. Pat. 3,476,563, the thiocyano group illustrated by the 4-thi0- phenols and 4-thionaphthols of Loria U.S. Pat. 3,253,924, the cyclic irnido groups as illustrated by the 4-cyclic irnido derivatives of 1-hydrogen-2-naphthamides of Loria U.S. Pat. application 504,994, now U.S. Pat. 3,458,315, the chlorine atom as illustrated in the 4-chlorophenols of Weissberger U.S. Pat. 2,423,730, the alkoxy group and the arylthio group as illustrated by the 4-alkoxynaphthols and 4-arylthiophenols (and naphthols) of Whitmore et al. U.S. Pat. 3,227,550, the sulfo group as in 4-sulfophenols and 4-sulfonaphthols, etc.

The 2-equivalent cyan-forming couplers used according to my invention include those having the formulas:

wherein R R R and R are as defined previously; Y represents the groups previously defined for Y but does not represent an aryloXy group; Y represents the groups previously defined for Y and also includes a cyclic irnido group (e.g., a maleimido group, a succinimido group, a 1,2-dicarboximido group, a phthalimido group, etc.).

Typical examples of 2-equivalent cyan-forming couplers include the following illustrative couplers:

( l 1-hydr0xy-4- 3-octadecylcarboxyphenylthio N-ethyl-3 ,5-dicarboXy-2-naphthamide (2) 2-pentadecylureylene-4-sulfophenyl (3) 4-sulfo-2-tetradecylureylene naphthol (4) 2- [Z-(hexadecyloxyphenyl) carbamyl1-4-sulfonaphthol (5) 1-hydroxy-N-{4-[5- (Z-carboxy-x-chlorosulfamyl) 2-(2,4-di-t-amylphenoxy) benzamido phenethyl}- 4-chloro-2-naphthamide (6) 1-hydroXy-2,5-dibutoXy-4- [4-(sulfomethyl) phenylazo1-2-naphthanilide 7) 1-hydroXy-4- 3 -octadecy1carbamylphenylthio) -N- methyl-N- S-carboxyethyl) -2-naphthanilide (8) l-hydroxy-4-acetoxy-N- 6- 2,4-di-t-amylphenoxy) butyl] naphthamide and VIII.

Any non-modified gelatin having an isoelectric point of at least 6.5 is used advantageously according to my invention. These gelatins are generally produced by processing collagen stock in dilute acid in a manner well known in the art. The collagen stock is obtained advantageously from the usual sources including animal bones, hides, swim bladder, etc. These gelatins have isoelectric points that are generally in the range from above about 6.5 to 11 plus.

My photographic color coupling compositions comprise at least one of my color-forming couplers and at least one gelatin having an isoelectric point of at least 6.5. Usually my compositions are prepared by intimately mixing the coupler in an aqueous solution of the gelatin so that the coupler is uniformly dispersed in the gelatin. Any of the well-known dispersing and blending equipment can be used to accomplish this. The ratio of the ingredients in the gelatin can vary widely. Generally speaking, the dispersion will contain about equal parts by weight of my acid treated gelatin and coupler but the ratio of these ingredients can vary widely as can the water content in the dispersion. The usual ratio of gelatin to coupler is in the range from about /1 to about /2 but can be more or less depending on the particular coupler, the nature of the emulsion, etc. The widest practical ratio of gelatin to couplers is in the range from about 1/5 to 70/1. The ratio of water to the dry ingredients can vary as desired from just enough to form a meltable mass to dilute solutions.

The amount of gelatin-coupler dispersion used in a final emulsion or photographic element can vary widely. The gelatin-coupler dispersion can be coated as a separate layer on a suitable support usually in contact with a lightsensitive photographic silver halide emulsion or more commonly incorporated in the light-sensitive silver halide emulsion and coated with it on the support. The silver halide emulsion is made with conventional photographic gelatin prepared by the lime process which has an isoelectric point below 6.5. My acid treated gelatins having an isoelectric point of at least 6.5 are not advantageously used in preparing the silver halide emulsion per se since they have a desensitization afrect upon the light-sensitive silver halide. However, after the silver halide emulsion is made with the low isoelectric point gelatin my gelatincoupler dispersion is advantageously added and does not produce any change in the original sensitivity of the lightsensitive silver halide. The high viscosity problems that one would get by using the conventional lime process, low isoelectric gelatins for dispersing the Fischer couplers is avoided by the use of my acid prepared gelatins having an isoelectric point of 6.5 or above in the preparation of the gelatin-coupler dispersion.

The emulsions used in my photographic elements may contain silver chloride, silver bromide, silver iodide, silver chloroiodide, silver bromoiodide, silver chlorobromoiodide, etc., as the light-sensitive material. A silver halide is dispersed in any of the hydrophilic colloids used for this purpose in photography including gelatin (usually from lime processed collagen, so the gelatin has an isoelectric point below 6.5), colloidal albumin, a cellulose derivative or a synthetic resin, for instance, a polyvinyl compound. My emulsions are advantageously optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker U.S. Pats. 1,846,301; 1,846,302;

and 1,942,854; White US. Pat. 1,990,507; Brooker and 6 White U.S. Pats. 2,112,140; 2,165,338; 2,493,747; and 2,- 739,964; Brooker and Keyes US. Pat. 2,493,748; Sprague U.S. Pats. 2,503,776; 2,519,001; Heseltine and Brooker U.S. Pats. 2,666,761; Heseltine U.S. Pat. 2,734,900; Van- Lare US. Pat. 2,739,149; Kodak Limited British Pat. 450,958. My emulsions also advantageously contain any of the other emulsion addenda well-known in the art including chemical sensitizers, antifoggants, hardening agents, coating aids, etc.

The invention is illustrated in the following examples which include specific and preferred embodiments.

EXAMPLES 1-6 A two percent aqueous solution of color coupler is prepared and heated to 125 F. To the solution is added 70 gms. of a ten percent gelatin solution and the mixture stirred for five minutes. To this is added 7 cc. of a 7.5 percent solution of saponin coating aid. The volume is adjusted to 250 cc. with water. The resulting mixture is cooled to F. and the pH adjusted to about 6-6.5 with any acid or base as necessary. The nature of the gelatin and the nature and amount of the coupler solution is varied in these examples as illustrated in the following table which also shows the viscosity of the compositions.

Coupler I.l-hydroxy--(3-octadecylcarbamylphenylthio)-N-cthyl-3', 5-dicarboxy-2-naphthanilide:

(])H C 0 OH @C ONHCraHg Coupler II.-l-(4-sullophenyl)-3-(4sulfoanilino)-4-(2-hydroxy-4-pentadccylphcnylazo) -5pyrazolone, dipotassium salt:

COOH

Coupler III.rz-PiV2-1yl-a- (3-octadeeylcarbamylph enylthio) 4-sultoacetanilide, potassium salt:

011930 c o 1110 ONE-@8031;

Coupler I is a cyan coupler which includes two carboxylic acid solubilizing groups and a C alkyl ballast group linked through a phenylthio group to the coupling atom of the naphthol ring. The coupler is of the elimination coupling, or 2-equivalent type and it will be noticed that the ballast group is attached to that portion of the coupler which is split from the dye portion during development. Accordingly, after photographic development, the dye is capable of diffusing. Coupler II is a magenta coupler which also includes an alkyl ballast group (C and potassium sulfonate solubilizer groups. The ballast group is attached to the coupler through a phenylazo group which is split from the coupling atom of the pyrazolone coupler during development. Coupler III is a yellow acetanilide coupler which includes a potassium sulfonate solubilizing group and a C alkyl ballast group attached to the reactive center through a phenylthio group which is split ofi during coupling. These and related couplers are more fully described in U.S. Pats. No. 3,227,- 551 and No. 3,265,506.

As shown in Table I, the viscosity of the coupler dispersions in pigskin gelatin is considerably less than that of the respective coupler dispersions in bone gelatin which is obtained by the liming process and which has an isoelectric point of about 5. The pigskin gelatin, on the other hand, was obtained by acid treatment of pigskin and the isoelectric point is at least 6.5, being about 7.5 in the example. Similar results are obtained using gelatin derived from the usual sources including animal bones and hides. Gelatin is obtained by first subjecting the collagen stock to a liming or acid process followed by cooking to extract the gelatin. Gelatins produced by the liming process, such as photographic gelatin obtained from calfskin, generally have an isoelectric point of about 4.7 to 5. Gelatins obtained from acid processing have a higher isoelectric point which, for example, can be 8.2 in the case of pigskin gelatin, 11 in the case of swim bladder gelatin, etc. In any event, it is possible by processing collagen stock in dilute acid in a manner known per se, to produce gelatin having an isoelectric point of at least 6.5 or higher such as an isoelectric point of at least 7.0. The pH of the dispersions (or blends) according to the foregoing examples of the invention is adjusted as necessary to be lower than the isoelectric point of the acid treated pigskin gelatin. The adjusted pH is in the range between about 6.0 and about 6.5 as shown since this is the preferred pH range for photographic emulsions to which the coupler gelatin blend is added. the pH of the blend, however, can vary from this preferred range and may be, e.g., in the range from about 5 to about 7. However, in accordance with the invention, the isoelectric point of the gelatin used in the dispersion should be higher than the pH of the dispersion and at least 6.5. The isoelectric point of acid processed pigskin gelatin, for example, is generally about 7.5 which renders this material useful according to the invention in dispersions having a pH range of from 5 to 7. As mentioned, the pH range of the dispersion is generally from 5 to 7, still more preferably 6 to 6.5, since the dispersion is intended to be incorporated in photographic gelatin silver halide emulsions which generally have a pH within these ranges. The incorporation of my dispersions of solubilized couplers in gelatin having an isoelectric point of at least 6.5 in photographic emulsions is illustrated in the example which follows.

EXAMPLE 7 A multilayer color film was prepared as follows:

(1) Red-sensitive cyan dye-forming emulsion layer A subbed cellulose ester film support is coated with a red-sensitive direct positive emulsion layer containing the cyan coupler I as follows:

To one mole of a melted, internal-image, direct-positive silver bromoiodide emulsion of the type described in U.S. Pat. 2,592,250 which has been red-sensitized, is added 108.0 grams of the cyan coupler I in 2500 cc. of water and 108.0 grams of acid-processed pigskin gelatin having an isoelectric point of about 8 to make a total of 139.0 grams of gelatin per mole of silver. This emulsion is then coated so as to obtain 0.193 g. gelatin, 0.150 g. coupler and 0.150 g. silver per sq. ft.

(2) Interlayer To 4540 grams of a 10 percent photographic gelatin solution is added 250 grams of the antioxidant, 2-octadecyl-4-sulfohydroquinone-mono-K-salt, in 5000 cc. of hot water. This is coated to obtain 0.091 g. gelatin and 0.050 g. of the antioxidant per sq. ft.

(3) Green-sensitive magenta-forming emulsion layer To one mole of a melted, internal-image, direct-positive silver bromoiodide emulsion of the type described in U.S. Pat. 2,592,250, which has been green-sensitized, is added 81 grams of the magenta coupler II in 3000 cc.

of Water and 81 grams of acid-processed pigskin gelatin to make a total of 162 grams of gelatin per mole of silver. This solution is coated so as to obtain 0.180 g. gelatin, 0.090 g. coupler II and 0.120 g. silver per sq. ft.

(4) Filter layer To 4540 grams of a 10 percent photographic gelatin solution is added 250 grams of the antioxidant mentioned above in 5000 cc. of hot water and 4.0 grams of yellow Carey Lea silver as a dispersion. This solution is then coated to obtain 0.091 g. gelatin, 0.050 g. antioxidant and 0.008 g. Carey Lea silver per sq. ft.

(5) Blue-sensitive yellow-forming emulsion layer To one mole of a melted, internal-image, direct-positive silver bromoiodide emulsion of the type described in U.S. Pat. 2,592,250, which is inherently blue light-sensitive, is added 144 grams of coupler III which had been dissolved in 750 cc. of ethyl alcohol and 3000 cc. of water and 100 grams of acid-process pigskin gelatin to make a total of 118 grams of gelatin per mole of silver. This solution is coated so as to obtain 0.161 g. gelatin, 0.200 g. coupler III and 0.150 g. silver per sq. ft.

(6) Protective layer Developer for internal latent image emulsion Ascorbic acid0.4 g.

4-amino-N-ethyl-N-(ti-hydroxyethyl) -aniline--l0.0 g.

Benzotriazole-0.l g.

p-Methylsulfonamidoethyl phenyl hydrazine hydrochloride---.3v g.

Sodium hydroxidel4.0 g.

Water300.0 cc.

The above ingredients are dissolved in the water, then the whole added to 700 g. of a 4 percent aqueous solution of alkali-soluble carboxymethylcellulose. The resulting sandwich is maintained at a temperature of F. for about 5 minutes after which the emulsion is separated from the receiving sheet to obtain a direct positive image of the subject in full color on the receiving sheet. Additional prints are obtainable in the same manner by again rolling the film into contact with fresh reception sheets and additional quantities of viscous developer. The mordanted reception sheet includes a paper base on which is coated a gelatin solution of a mixture of the quaternary ammonium salt mordants dimethyl-B-hydroxyethyl-w ,(octadecylamido) -propyl ammonium dihydrogen phosphate and distearyl dimethyl-ammonium chloride, so as to obtain 75 mg. of each mordant and mg. of gelatin per sq. ft. In the development process above, each of the emulsion layers is developed in the positive (un exposed) region by virtue of the hydrazine compound of the developer neutralizing the charges on the imageexposed silver halide grains and also nucleating (fogging) the unexposed grains so that they develop, with the result that the oxidized developing agent produced thereby causes each of the cyan, magenta and yellow dye-forming couplers to split at the coupling position and the coupler moieties thus released each to form a ditfusible dye with the oxidized developer, which dyes then diffuse image- Wise in register to the reception sheet to form a multicolor positive image thereon.

My dispersions of couplers (having acid solubilizing groups )in gelatin having an isoelectric point of at least 6.5 are used advantageously wherever couplers are required in the various photographic elements described in Whitmore et al. US. Pat. 3,227,550, as well as in any photographic elements that require incorporated couplers for forming non-difiusible dye images in the photographic element. These elements may be designed for making colored negatives as in negative-positive color systems (using a color development process such as is described in Example 2 of Loria US. Pat. 3,311,476, or in Canadian Patent 726,137), or for making color prints in a reversal color system (using a color reversal process such as is described by Example (a) in Graham and Sagal US. Pat. 3,046,129). In these processes, any of the well-known primary aromatic amino color-forming silver halide de veloping agents, such as, the phenylenediamines, e.g., diethyl-p-phenylenediamine hydrochloride, monomethylp-phenylenediamine hydrochloride, dimethyl-p-phenylenediamine hydrochloride, 2-amino-S-diethylaminetoluene hydrochloride, 2-amino-5-(N-ethyl-N-lauryl) toluene, N- ethyl-B-methanesulfonamidoethyl 3 methyl 4 amino aniline sulfate, N-ethyl-B-methanesulfonamidoethyl-4- aminoaniline, 4 N ethyl-N-p-hydroxyethylaminoaniline, etc., p-amino phenols and their substitution products where the amino group is unsubstituted are used.

My Fischer coupler dispersions in acid treated gelatins having an isoelectric point of at least 6.5 provide a valuable technical advance in the art of color photography because they have substantially lower viscosities than the conventional dispersions of the same couplers in the photographic gelatins normally used. My compositions make it possible to make better dispersions of the couplers and greatly facilitate their preparation and coating in the manufacture of photographic products. Acid treated gelatins having an isoelectric point of at least 6.5 are not normally used in photography because of the desensitization they product in light-sensitive silver halide. In the immediate invention the silver halide emulsion is made with conventional photographic gelatin prepared by the lime process and subsequently my dispersion of the Fischer coupler in the acid prepared gelatin having an isoelectric point of 6.5 or higher is added to the emulsion. In this Way, the acid prepared gelatin does not produce any desensitizing aifects on the silver halide and the high viscosity problems that one would get by using lime process gelatins in dispersing the Fischer couplers is avoided.

The invention has been described in detail with particular embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A photographic color coupler composition comprising a non-difiusing color coupler dispersed with gelatin produced by processing collagen in dilute acid, said gelatin having an isoelectric point of at least 6.5, said coupler containing at least one acid solubilizing group and being capable of reaction with the oxidation product of. a primary aromatic aminocolor -forming silver halide developing agent to form a dye, the weight ratio of said gelatin to said coupler being in the range of from about 12 1:5 to about 70:1, said dispersion having a substantially lower viscosity than identical dispersions of the same coupler With gelatin having an isoelectric point lower than 6.5.

2. A composition of claim 1 in 'Which the gelatin has an isoelectric point in the range of from about 6.5 to about 11.

3. A composition of claim 1 wherein the ratio of gelatin to coupler is in the range of from about 1:5 to about 10:1.

4. A composition according to claim 1 having a pH of from about 5 to about 7, the isoelectric point of said gelatin being higher than the pH of the composition.

5. A composition according to claim 1 having a pH of from about 6 to about 6.5, the isoelectric point of said gelatin being higher than the pH of the composition.

6. A composition of claim 1 in which the coupler is a non-diifusing open-chain active methylene containing yelloW-dye-forming coupler.

7. A composition of claim 1 in which the coupler is a non-diffusing S-pyrazolone magenta-dye-forming coupler.

8. A composition of claim 1 in which the coupler is a non-diffusing cyan-dye-forming coupler selected from the class consisting of a phenolic coupler and a naphthoic coupler.

9. A photographic element comprising at least one lightsensitive gelatin-silver halide photographic emulsion and, in contact with said emulsion, a composition as claimed in claim 1.

10. A composition comprising coupler 1-hydroxy-4-(3- octadecyclcarbamylphenylthio)-N-ethyl-3',5 dicarboxy- 2 naphthanilide dispersed with acid processed pigskin gelatin having an isoelectric point of 7.5, said gelatin and said coupler having a weight ratio of 2:1, said composition having substantially lower viscosity than identical compositions of said coupler with gelatin having an isoelectric point lower than 6.5.

11. A composition comprising coupler l-(4-sulfophenyl)-3-(4-sulfoanilino)-4-(2-hydroxy 4 pentadecylphenylazo)-5-pyrazolone, dipotassium salt dispersed with acid-processed pigskin gelatin having an isoelectric point of 7 .5, said gelatin and said coupler having a weight ratio of 5:2, said composition having a substantially lower viscosity than identical compositions of the same coupler with gelatin having an isoelectric point lower than 6.5.

12. A composition comprising coupler a-pivalyl-a-(3- octadecylcarbamylphenylthio) -4 sulfoacetanilide, potassium salt dispersed with acid-processed pigskin gelatin having an isoelectric point of 7.5, said gelatin and said coupler having a weight ratio of about 1.421, said composition having a substantially lower viscosity than identical compositions of the same coupler with gelatin having an isoelectric point lower than 6.5.

13. A multilayer color film which has a red-sensitive gelatin silver halide emulsion layer that is in contact with a dispersion of Coupler I, 1-hydroxy-4-(3-octadecylcarbamylphenylthio)-N-ethyl-3',5 dicarboxy 2 naph thanilide, in acid-treated pigskin gelatin having an isoelectric point of 7 .5, a green-sensitive gelatin silver halide emulsion layer that is in contact with a dispersion of Coupler II, l-(4-sulfophenyl)-3-(4-sulfoanilino)-4-(2 hydroxy-4-pentadecylphenylazo)-5 pyrazalone, dipotassium salt, in acid-treated pigskin gelatin having an isoelectric point of 7.5, and a blue-sensitive gelatin silver halide emulsion layer that is in contact with a dispersion of Coupler III, a-pivalyl-u-,(3-octadecylcarbamylphenylthio)-4-sulfoacetanilide, potassium salt in acid-processed pigskin gelatin having an isoelectric point of 7 .5, said dispersion of Coupler I, said dispersion of Coupler II and said dispersion of Coupler III, each having a substantially lower viscosity than identical dispersions made of the respective couplers, but with gelatin having an isoelectric point lower than 6.5.

13 14. In a method for preparing a light-sensitive gelatin silver halide photographic emulsion containing an incorporated non-diffusing color-forming coupler having at least one acidic solubilizing group, the improvement comprising:

(1) the use of a dispersion of said coupler with acidprocessed gelatin having an isoelectric point of at least 6.5, said dispersion having a substantially lower viscosity than identical dispersions made of said coupler with gelatin having an isoelectric point lower than 6.5, said dispersion having a weight ratio of said gelatin with an isoelectric point of at least 6.5 to coupler in the range of from about 1:5 to about 70: 1; and then (2) incorporating the dispersion of said coupler in said gelatin having an isoelectric point of at least 6.5 in the said light-sensitive gelatin silver halide emulsion prepared with gelatin having an isoelectric point lower than 6.5.

References Cited UNITED STATES PATENTS FOREIGN PATENTS 5/ 1962 Great Britain.

OTHER REFERENCES Making and Coating Photographic Emulsions, Zelikman and Levi, 1964, The Focal Library, pp. 245-247.

15 NORMAN G. TORCHIN, Primary Examiner J. R. HIGHTOWER, Assistant Examiner US. C. X.R. 

